The circuit card module is a well known form of electric circuit packaging in which a series of individual circuit cards is each removably mounted to a chassis. Each circuit card carries at one end a set of electrical contacts adapted to engage a mating set of contacts mounted to the chassis. The increasing variety of applications for such modules requires improved performance and adaptability to a variety of environments. For example, greater circuit complexity results in an increase in the number of electrical pin contacts, frequently to over one hundred pins per circuit card. The force required for inserting the card into the chassis then can exceed one hundred pounds. Along with the greater insertion force, there remains the need for insertion accuracy since the contact pins individually are delicate and susceptible to bending or breakage. One method of accommodating the insertion requirement is shown in U.S. Pat. No. 3,848,953 to Petroshanoff granted Nov. 19, 1974, showing a jackscrew which, when threaded into a guide, brings the male and female contacts of the circuit card and housing together in alignment. Another method is to make at least one set of electrical contacts movable with respect to its carrier, i.e., either the circuit card or the chassis. U.S. Pat. No. 3,853,379 to Goodman et al granted Dec. 10, 1974, is an example of such an approach.
As modules are employed in increasingly hostile environments, the need arises to reduce or eliminate circuit card vibration with respect to the chassis. U.S. Pat. No. 3,922,051 granted to Reynolds, Nov. 25, 1975, shows a wedge driven between a visual display panel and an upper ledge to force a series of contacts against mating contacts in a lower ledge.
Yet another performance requirement of the circuit module is rapid heat dissipation. The individual electrical components generate heat as they dissipate power. Heat buildup is aggravated by the increased density of components upon each circuit card and the density of cards in the chassis. One method of heat dissipation is shown in U.S. Pat. No. 3,845,359 to Fedele granted Oct. 29, 1974, showing a circuit card anchor which includes a heat conducting spring held between ends of a beam and compressable against the side flanges of a chassis wall, thereby to provide improved heat conduction between the circuit card and the chassis walls.
There are particular uses for circuit modules which entail extreme environmental conditions, particularly in the fields of aviation and space exploration. These require yet further improvements in accurate, positive circuit card mounting and heat dissipation. It is an object of this invention, therefore, to eliminate any substantial vibration in the circuit card relative to its chassis. It is a further object of the invention to provide a guide for aligning mating electrical contacts of a chassis and circuit card prior to the actual engagement of the contacts. Yet another object of the invention is to provide a firm mounting of each circuit card within the chassis and maximize the transfer of heat from each circuit card in the chassis.